PTC Heating Element Diagnosis via Current Curve Segmentation
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Solution Overview
Problem
Existing methods for diagnosing the functionality of electric heating devices with PTC-elements in HWL-tanks are inaccurate, particularly when multiple elements are connected in parallel, leading to misdiagnoses due to high tolerances and environmental factors like fluid levels and pressures, which affect current flow and temperature dynamics.
Innovation Solution
A procedure that compares measured current values against reference values, considering battery voltage and temperature, to detect deviations and determine the functionality of PTC-elements, using the characteristic current course curve to identify errors and differentiate between malfunctioning or short-circuited elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional power switch with current mirror is used for diagnosis, then the heating device can be checked electrically, but the diagnosis accuracy deteriorates due to high tolerances and inability to distinguish error types
Solution Approach 1:
The patent segments the diagnosis process into multiple measurement points along the characteristic current curve (initial current peak, current at specific time points, steady-state current). By measuring at multiple segments of the current flow through parallel PTC-elements, the system can identify which specific element or connection is faulty, transforming a single inaccurate measurement into multiple precise diagnostic data points that can be individually evaluated against reference values.
2Reliability
If parallel interconnected PTC-elements are used for heating, then the heating coverage is improved, but the difficulty of detecting and measuring individual element status worsens
Solution Approach 1:
The patent implements feedback by continuously monitoring the current flow through the parallel PTC-elements and comparing it against the characteristic current course curve. The control unit receives feedback about the actual current at multiple time points and uses this feedback to determine whether each individual element or their connections are functioning properly, enabling precise identification of faults in parallel configurations.
3Adaptability or versatility
If battery voltage fluctuations are present, then the electrical system adapts to varying conditions, but the measurement accuracy deteriorates without voltage compensation
Solution Approach 1:
The patent applies parameter changes by using the actual battery voltage as a variable parameter that directly influences the reference current course curve. Instead of using fixed reference values, the system adjusts the reference curve based on the measured battery voltage, accounting for voltage fluctuations. This ensures that current measurements remain accurate and comparable even when the electrical system adapts to varying voltage conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides a reliable method for diagnosing the functionality of electric heating devices, ensuring accurate detection of performance issues and preventing misdiagnoses by accounting for battery voltage fluctuations and temperature variations, thereby ensuring reliable heating power delivery for SCR systems in diesel vehicles.
Implementation Method 1
electric current can be converted into heat. Therefore two ohmic heating elements can be for example provided
Implementation Method 2
Positive temperature coefficient thermistor comprise current conducting materials, which conduct the current better at lower temperatures than at higher temperatures. The electric resistance increases with an increasing temperature
Data Source
AI summary
A procedure for checking the functionality of an electric heating device (10) with at least one PTC-element (13, 14) is suggested. The electric heating device (10) is operated at a battery voltage. When controlling the heating device (10) it is impinged with a current and at least one measuring value is detected, which represents the current that flows through the heating device. The measuring value for the current is compared to at least one reference value with a default tolerance width while considering the battery voltage. In the case of a measuring value that deviates from the reference value an error can be assumed.